Steel SS400
JIS SS400
SS400 is the base grade of JIS G3101 general-purpose hot-rolled structural carbon steel, specified mainly by mechanical properties (≥245 MPa yield, 400–510 MPa tensile) with only P and S limited chemically.
Values for the HR condition
SS400 tempers and conditions
SS400 is supplied in 4 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
subcritical/full anneal for maximum ductility | Used for deep-drawn or severely bent parts and for stress relief of weldments; lowest hardness, poorest surface-finish machining behaviour. | 250 | 420 | 33 | 110 HB | 11 % IACS |
880–920 °C air cool (grain refinement of thick plate) | Occasionally ordered for thick plate or after heavy forming/flame cutting to refine grain and even out toughness; strength stays in the SS400 band. | 270 | 440 | 30 | 120 HB | 10.8 % IACS |
HRDefault Hot rolled | Default stock condition for plate, bar, angle and structural sections; cheapest, mill-scale surface, dimensional tolerances loose. | 280 | 450 | 26 | 125 HB | — |
Cold rolled | Pick when a bright scale-free surface, tight thickness/diameter tolerance and higher yield are needed; ductility and bendability are reduced. | 380 | 500 | 16 | 150 HB | — |
Supply forms, finishes and certifications
Ways SS400 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
Galvanized | Hot-dip zinc coated | Coating |
What is SS400?
SS400 is the base grade of JIS G3101 general-purpose hot-rolled structural carbon steel, specified mainly by mechanical properties (≥245 MPa yield, 400–510 MPa tensile) with only P and S limited chemically. It is chosen for frames, brackets, base plates, machine bases and weldments where cost, weldability and formability matter more than strength or toughness. Limits: no impact-energy or fine-grain requirement, poor corrosion resistance (must be painted, galvanized or plated), not heat-treatable to higher strength, and property scatter between mills/heats is larger than for alloy steels. SS400 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). SS400 has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 90% of steel grades. Elongation at break is 26% and the elastic modulus is 205 GPa (29.7 Msi).
What is SS400 used for?
- Welded structures
- Bridges
- Building frames
Advantages
- High electrical conductivity — 10.8 % IACS, better than 94% of steel grades
- Easy to machine — 65/100, better than 93% of steel grades
- Readily welded — 92/100, better than 93% of steel grades
- Conducts heat well — 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades
- Forms and bends easily — 78/100, better than 91% of steel grades
Limitations
- Low strength — 280 MPa (40.6 ksi), worse than 90% of steel grades
- Hard to polish — 45/100, worse than 84% of steel grades
SS400 properties
Typical room-temperature values for SS400-HR; bars are the position among steel grades.
Physical3
SS400 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
SS400 has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 90% of steel grades. Elongation at break is 26% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SS400 is rated for continuous service to 350°C (662 °F). It conducts heat at 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
SS400 conducts electricity at 10.8 % IACS, better than 94% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of SS400 takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability8
SS400's machinability is good (65/100, better than 93% of steel grades); weldability excellent (92/100); formability very good (78/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. SS400 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SS400
Is SS400 easy to machine?
Cuts easily but gummy: use sharp positive-rake tooling, 100–200 m/min carbide, generous coolant and chip breakers to avoid built-up edge and stringy chips.
Can SS400 be welded?
Excellent weldability by SMAW/GMAW/FCAW/SAW with E7018 or ER70S-6; no preheat needed below roughly 25 mm section at room temperature — strip zinc back on galvanized stock and ventilate.
Can SS400 be formed, bent or molded?
Hot-rolled sheet bends readily to ~1.5×t inside radius (2–3×t for cold-rolled or galvanized); roll, press-brake and stamp cold, hot-form above 900 °C for heavy sections.
Manufacturability
The process limits FabDigit's quote engine applies to SS400. Design inside these and the part quotes instantly; outside them it routes to an engineer.
CNC machining
| Machinability | Better65 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Excellent78 / 100 |
|---|---|
| Weldability | Excellent92 / 100 |
| Bendable | Yes |
SS400 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Cnot specified by JIS G3101 for SS400; mills typically 0.10–0.25 % | ≈ 0.17 | 0.17 |
| Sinot specified; typically ≤0.35 % | ≈ 0.2 | 0.2 |
| Mnnot specified; typically 0.30–0.80 % | ≈ 0.55 | 0.55 |
| PJIS G3101 limit (0.050 max) | ≤ 0.05 | 0.02 |
| SJIS G3101 limit (0.050 max) | ≤ 0.05 | 0.02 |
| Fe | balance |
What surface finishes work on SS400?
Not anodizable — remove mill scale by shot blast or pickling, then paint, phosphate+oil, zinc plate, hot-dip galvanize or powder coat; bare steel rusts within days indoors if humid.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel SS400 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- common structural steel
How much does SS400 cost?
SS400 is a budget-cost steel ($), cheaper than about 99% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
SS400 — frequently asked
What is SS400 used for?
SS400 is typically used for welded structures, bridges and building frames. In short: workhorse Japanese mild plate.
What is the yield strength of SS400?
SS400 has a typical yield strength of 280 MPa (40.6 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 90% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is SS400 easy to machine?
Reasonably — machinability is rated good (65/100, better than 93% of steel grades). Cuts easily but gummy: use sharp positive-rake tooling, 100–200 m/min carbide, generous coolant and chip breakers to avoid built-up edge and stringy chips.
Can SS400 be welded?
Yes — weldability is rated excellent (92/100). Excellent weldability by SMAW/GMAW/FCAW/SAW with E7018 or ER70S-6; no preheat needed below roughly 25 mm section at room temperature — strip zinc back on galvanized stock and ventilate.
What surface finishes work on SS400?
Not anodizable — remove mill scale by shot blast or pickling, then paint, phosphate+oil, zinc plate, hot-dip galvanize or powder coat; bare steel rusts within days indoors if humid.
Can SS400 be formed, bent or molded?
Hot-rolled sheet bends readily to ~1.5×t inside radius (2–3×t for cold-rolled or galvanized); roll, press-brake and stamp cold, hot-form above 900 °C for heavy sections.
What is the maximum service temperature of SS400?
SS400 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SS400-HR and SS400-CR?
HR is the default condition — default stock condition for plate, bar, angle and structural sections; cheapest, mill-scale surface, dimensional tolerances loose. CR: pick when a bright scale-free surface, tight thickness/diameter tolerance and higher yield are needed; ductility and bendability are reduced. Yield strength is 280 MPa in HR versus 380 MPa in CR.
How much does SS400 cost?
SS400 is a budget-cost steel ($), cheaper than about 99% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in SS400?
Yes — SS400 is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- JIS G3101 — Rolled steels for general structure — Japanese Standards Association (2020)
- GB/T 700 — Carbon structural steels (Q235B comparison) — SAC (2006)
- ASTM A36/A36M — Carbon structural steel — ASTM (2019)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook, 31st ed. (machinability ratings) — Industrial Press (2020)
- worldsteel LCI data for hot-rolled coil and plate — World Steel Association (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.